This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. P2001-34156 filed on Feb. 9, 2001 and No. P2001-60581 filed on Mar. 5, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a method of manufacturing semiconductor devices with the use of a wafer carrier having conditioning units. The wafer carrier stores in-process wafers and carries them between manufacturing equipments on a semiconductor device manufacturing line.
2. Description of the Related Art
Semiconductor devices having fine patterns are manufactured in a clean room free of dust. A clean room, however, still contains or produces impurities that affect semiconductor device manufacturing processes. Chemical filters to remove impurities from intake air are therefore employed, and other chemical filters are installed in air conditioners and air circulating systems to remove impurities produced in the clean room.
In-process wafers handled in the clean room are stored and carried in a wafer carrier to prevent dust or impurities from making contact with the wafers. Some semiconductor device manufacturing processes carried out in the clean room leave residues on the wafers which contaminate other wafers when they are stored in the wafer carrier.
To solve this problem, Japanese Patent Laid Open Publication No. 7-94577 discloses a technique of using a vapor removing element having an activated carbon absorption layer to remove chemical vapors (impurities) from a wafer carrier. Ebara Corporation has marketed a wafer carrier xe2x80x9cWafer Carrying Clean Box (trade name)xe2x80x9d having a chemical filter to remove impurities and a fan to circulate air in the wafer carrier.
A semiconductor device manufacturing line includes processes that leave a large amount of residue on wafers. If wafers contaminated with the residues are stored in a wafer carrier, the residues will quickly destroy the chemical filter installed in the wafer carrier.
The wafer carriers in the related art are only capable of maintaining a single operating condition throughout a semiconductor device manufacturing line. In practice, a manufacturing line involves various processes some of which require wafers in a wafer carrier to be at low humidity, some of which require wafers in a wafer carrier to be free of impurities, and some of which require wafers in a wafer carrier both to be free of humidity and impurities. These requirements must be met to improve the quality and yield of semiconductor devices manufactured. The related art are incapable of flexibly meeting such varied requirements.
Ion-impurity removing chemical filters rapidly deteriorate in their performance when environmental humidity drops below 20%. Chemical filters remove ion impurities with difficulty in low humidity.
In this way, the semiconductor device manufacturing line involves processes having various requirements, and the chemical filters dysfunction in low humidity. To properly store and carry wafers through various processes in the semiconductor device manufacturing line in the related art, wafer carriers of different functions must be prepared and changed from one to another depending on processes. This increases the purchasing cost of the wafer carriers. In addition, vacant wafer carriers must be allocated to various semiconductor device processes depending on the characteristics of the wafer carriers and processes, increasing delivery load. These wafer carriers need large storage spaces and must be switched from one to another depending on the process, thus extending manufacturing time.
The wafer carriers require batteries to drive the fans and dehydrate the filters installed in the wafer carriers. The batteries usually last for only about {fraction (1/100)} of the semiconductor device manufacturing time, and therefore, must be recharged. Recharging is troublesome, may delay the manufacturing schedule, and needs a recharging space.
The relative humidity in a clean room is usually maintained at between 30% to 60% for the workability of workers and the performance of chemical filters. The humidity in a clean room promotes the formation of natural oxide films on wafers which corrode the metal wiring formed on the wafers.
According to an aspect of the present invention, a method of manufacturing semiconductor devices uses a wafer carrier having conditioning units to control internal conditions of the wafer carrier. The wafer carrier stores wafers and carries them between manufacturing equipments used in a series of semiconductor device manufacturing processes. For each of the manufacturing processes, the method includes placing the wafer carrier on a load port that automatically opens and closes a lid of the wafer carrier, transferring the wafers from the wafer carrier into the manufacturing equipment through the load port, changing operating conditions of the conditioning units of the wafer carrier according to a process or test being carried out by the manufacturing equipment on the wafers, returning the wafers into the wafer carrier through the load port after the completion of the process or test, and operating the conditioning units according to the changed operating conditions controlling the internal conditions of the wafer carrier until the wafer carrier with the wafers is carried to a manufacturing equipment of the next manufacturing process.
According to another aspect of the present invention, a system of manufacturing semiconductor devices includes manufacturing equipments carrying out a process or test on wafers in a series of manufacturing processes, a wafer carrier storing the wafers and carrying them between the manufacturing equipments, and a managing unit having a memory to store a sequence of the operating conditions for the series of manufacturing processes. The wafer carrier has conditioning units controlling internal conditions of the wafer carrier, and a display displaying a operating conditions of the conditioning units. The managing unit provides instructions to specify the operating conditions of the conditioning units.